Rainbow-electronics MAX5098A Manual de usuario descargar pdf (Pagina 23)

MAX5098A

Dual, 2.2MHz, Automotive Buck or Boost

Converter with 80V Load-Dump Protection

______________________________________________________________________________________ 23

3) Place a zero

where

and R

≥ 10kΩ.

4) Calculate C

for a target unity crossover frequency, f

5) Place a pole

or 5 x f

, whichever

is lower,

6) Place a second zero, f

, at 0.2 x f

or at f

whichever is lower.

7) Place a second pole at 1/2 the switching frequency.

Boost Converter Compensation

The boost converter compensation gets complicated

due to the presence of a right-half-plane zero

ZERO,RHP

. The right-half-plane zero causes a drop in

phase while adding positive (+1) slope to the gain

curve. It is important to drop the gain significantly below

unity before the RHP frequency. Use the following pro-

cedure to calculate the compensation components:

1) Calculate the LC double-pole frequency, f

, and

the right-half-plane-zero frequency.

where

OUT

MIN

OUT

OUT MAX

−

()

ZERO RHP

MIN

OUT

()

−

()

OUT OUT

××

−1

2π

fRC

SW F F

×× ××

()

−205 1π .

××

−

××

fL C V

C OUT OUT OSC

IN F

×× × ×

2π

LC F

×××

2075π .

at f

LC1

075=

××

COMP_

OUT

REF

FB_

Figure 5. Type III Compensation Network

PGND_

DRAIN_

MAX5098A

VDRV

V+

OUT_

BST_/VDD_

OUT

SGND

PGND_

DRAIN_

SOURCE_

FB_

Figure 6. Boost Application

at f

ZERO ESR1

××π

1 2 ... 18 19 20 21 22 23 24 25 26 27 28

MAX5098A 1

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Rainbow-electronics MAX5098A Manual de usuario Pagina 23

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